New drug shows promise for genital herpes

Scientists are reporting positive results with a new kind of drug to combat genital herpes, the first new treatment possibility in decades for the sexually transmitted disease that afflicts an estimated 50 million Americans.

In a study conducted in Houston and six other sites, researchers found that a daily 75-milligram dosage of the drug dramatically reduced the virus' ability to replicate and spread. There wasn't a comparable benefit from a placebo.

"This study represents a major a step forward in herpes research," said Dr. Stephen Tyring, a professor of dermatology at the University of Texas Health Science Center at Houston and the head of the research effort here. "The drug is still a few years from the market, but it should be a boon to the many people for whom existing therapy has lost effectiveness."

Dr. Anna Wald, a University of Washington virologist/epidemiologist and the lead author of the study, said she was most impressed by how potent the experimental drug proved to be. She said researchers are increasingly finding the existing drugs for herpes don't significantly reduce viral shedding, when herpes is most transmissible to sexual partners.

Genital herpes is one of the most common sexually transmitted diseases in the U.S., infecting roughly one in six Americans ages 14 to 49. Though it can cause pain and sores in the genital area, anal region and lips, patients frequently experience mild or no symptoms, leaving them unaware they're infected.

Existing treatment was developed in the 1980s and tweaked in the 1990s. It can shorten outbreaks, prevent recurrences and reduce transmission, but over time the virus has become more and more resistant to it.

The current drugs - acyclovir, valacyclovir and famciclovir - work by inhibiting a viral enzyme. The new drug, pritelivir, targets a different part of the virus' replication machinery earlier in the process.

The study, published in Thursday's New England Journal of Medicine, enrolled 156 patients who received either a placebo or four different dosage regimens of pritelivir for 28 days. The 75-milligram-a-day-dose was associated with an 87 percent reduction in the days of viral shedding.

A larger trial was planned for later this year, but at the moment further clinical research with the drug is on hold. The U.S. Food and Drug Administration suspended such research after monkeys given doses much greater than those in the new study showed some unexpected blood and skin abnormalities.